diff --git a/clang/lib/CodeGen/BackendUtil.cpp b/clang/lib/CodeGen/BackendUtil.cpp
--- a/clang/lib/CodeGen/BackendUtil.cpp
+++ b/clang/lib/CodeGen/BackendUtil.cpp
@@ -102,7 +102,7 @@
 
 // Default filename used for profile generation.
 std::string getDefaultProfileGenName() {
-  return DebugInfoCorrelate ? "default_%p.proflite" : "default_%m.profraw";
+  return DebugInfoCorrelate ? "default_%m.proflite" : "default_%m.profraw";
 }
 
 class EmitAssemblyHelper {
diff --git a/compiler-rt/lib/profile/InstrProfilingMerge.c b/compiler-rt/lib/profile/InstrProfilingMerge.c
--- a/compiler-rt/lib/profile/InstrProfilingMerge.c
+++ b/compiler-rt/lib/profile/InstrProfilingMerge.c
@@ -102,17 +102,10 @@
 COMPILER_RT_VISIBILITY
 int __llvm_profile_merge_from_buffer(const char *ProfileData,
                                      uint64_t ProfileSize) {
-  if (__llvm_profile_get_version() & VARIANT_MASK_DBG_CORRELATE) {
-    PROF_ERR(
-        "%s\n",
-        "Debug info correlation does not support profile merging at runtime. "
-        "Instead, merge raw profiles using the llvm-profdata tool.");
-    return 1;
-  }
-
   __llvm_profile_data *SrcDataStart, *SrcDataEnd, *SrcData, *DstData;
   __llvm_profile_header *Header = (__llvm_profile_header *)ProfileData;
-  char *SrcCountersStart;
+  char *SrcCountersStart, *DstCounter;
+  const char *SrcCountersEnd, *SrcCounter;
   const char *SrcNameStart;
   const char *SrcValueProfDataStart, *SrcValueProfData;
   uintptr_t CountersDelta = Header->CountersDelta;
@@ -122,14 +115,36 @@
                               Header->BinaryIdsSize);
   SrcDataEnd = SrcDataStart + Header->DataSize;
   SrcCountersStart = (char *)SrcDataEnd;
-  SrcNameStart = SrcCountersStart +
-                 Header->CountersSize * __llvm_profile_counter_entry_size();
+  SrcCountersEnd = SrcCountersStart +
+                 Header->CountersSize * __llvm_profile_counter_entry_size(); 
+  SrcNameStart = SrcCountersEnd;
   SrcValueProfDataStart =
       SrcNameStart + Header->NamesSize +
       __llvm_profile_get_num_padding_bytes(Header->NamesSize);
   if (SrcNameStart < SrcCountersStart)
     return 1;
 
+  // Merge counters when there is no data section and debug info correlation is
+  // enabled.
+  if (Header->DataSize == 0) {
+    if (!(__llvm_profile_get_version() & VARIANT_MASK_DBG_CORRELATE)) {
+      PROF_ERR("%s\n", "Missing profile data section.");
+      return 1;
+    }
+    for (SrcCounter = SrcCountersStart,
+        DstCounter = __llvm_profile_begin_counters();
+         SrcCounter < SrcCountersEnd;) {
+      if (__llvm_profile_get_version() & VARIANT_MASK_BYTE_COVERAGE) {
+        *DstCounter &= *SrcCounter;
+      } else {
+        *(uint64_t *)DstCounter += *(uint64_t *)SrcCounter;
+      }
+      SrcCounter += __llvm_profile_counter_entry_size();
+      DstCounter += __llvm_profile_counter_entry_size();
+    }
+    return 0;
+  }
+
   for (SrcData = SrcDataStart,
       DstData = (__llvm_profile_data *)__llvm_profile_begin_data(),
       SrcValueProfData = SrcValueProfDataStart;
diff --git a/compiler-rt/test/profile/Darwin/instrprof-debug-info-correlate.c b/compiler-rt/test/profile/Darwin/instrprof-debug-info-correlate.c
--- a/compiler-rt/test/profile/Darwin/instrprof-debug-info-correlate.c
+++ b/compiler-rt/test/profile/Darwin/instrprof-debug-info-correlate.c
@@ -18,3 +18,19 @@
 // RUN: llvm-profdata merge -o %t.cov.normal.profdata %t.cov.profraw
 
 // RUN: diff %t.cov.normal.profdata %t.cov.profdata
+
+// Test debug info correlate with online merging.
+
+// RUN: rm -rf %t.profdir && mkdir %t.profdir
+// RUN: %clang_pgogen -o %t -g -mllvm --debug-info-correlate -mllvm --disable-vp=true %S/../Inputs/instrprof-debug-info-correlate-main.cpp %S/../Inputs/instrprof-debug-info-correlate-foo.cpp
+// RUN: env LLVM_PROFILE_FILE=%t.profdir/%m.proflite %run %t
+// RUN: llvm-profdata merge -o %t.profdata --debug-info=%t.dSYM %t.profdir/
+
+// RUN: diff %t.normal.profdata %t.profdata
+
+// RUN: rm -rf %t.profdir && mkdir %t.profdir
+// RUN: %clang_pgogen -o %t.cov -g -mllvm --debug-info-correlate -mllvm -pgo-function-entry-coverage -mllvm --disable-vp=true %S/../Inputs/instrprof-debug-info-correlate-main.cpp %S/../Inputs/instrprof-debug-info-correlate-foo.cpp
+// RUN: env LLVM_PROFILE_FILE=%t.profdir/%m.cov.proflite %run %t.cov
+// RUN: llvm-profdata merge -o %t.cov.profdata --debug-info=%t.cov.dSYM %t.profdir/
+
+// RUN: diff %t.cov.normal.profdata %t.cov.profdata
diff --git a/compiler-rt/test/profile/Linux/instrprof-debug-info-correlate.c b/compiler-rt/test/profile/Linux/instrprof-debug-info-correlate.c
--- a/compiler-rt/test/profile/Linux/instrprof-debug-info-correlate.c
+++ b/compiler-rt/test/profile/Linux/instrprof-debug-info-correlate.c
@@ -24,3 +24,19 @@
 // RUN: llvm-profdata merge -o %t.cov.normal.profdata %t.cov.profraw
 
 // RUN: diff <(llvm-profdata show %t.cov.normal.profdata) <(llvm-profdata show %t.cov.profdata)
+
+// Test debug info correlate with online merging.
+
+// RUN: rm -rf %t.profdir && mkdir %t.profdir
+// RUN: %clang_pgogen -o %t -g -mllvm --debug-info-correlate -mllvm --disable-vp=true %S/../Inputs/instrprof-debug-info-correlate-main.cpp %S/../Inputs/instrprof-debug-info-correlate-foo.cpp
+// RUN: env LLVM_PROFILE_FILE=%t.profdir/%m.proflite %run %t
+// RUN: llvm-profdata merge -o %t.profdata --debug-info=%t %t.profdir/
+
+// RUN: diff <(llvm-profdata show %t.normal.profdata) <(llvm-profdata show %t.profdata)
+
+// RUN: rm -rf %t.profdir && mkdir %t.profdir
+// RUN: %clang_pgogen -o %t.cov -g -mllvm --debug-info-correlate -mllvm -pgo-function-entry-coverage -mllvm --disable-vp=true %S/../Inputs/instrprof-debug-info-correlate-main.cpp %S/../Inputs/instrprof-debug-info-correlate-foo.cpp
+// RUN: env LLVM_PROFILE_FILE=%t.profdir/%m.cov.proflite %run %t.cov
+// RUN: llvm-profdata merge -o %t.cov.profdata --debug-info=%t.cov %t.profdir/
+
+// RUN: diff <(llvm-profdata show %t.cov.normal.profdata) <(llvm-profdata show %t.cov.profdata)